3.1 Urban water supply system
This line item refers to the volume of water held in ACTEW's potable and non-potable water supply system. There are 47 tanks (service reservoirs) within ACTEW's supply system and approximately 3,140 km of pipes.
This volume is expected to remain relatively constant each year, with slight increases in pipe network volume due to the expansion of the network, and slight changes in the tank (service reservoir) volumes due to operational level changes.
The volume in the tanks (service reservoirs) was reported as the volume at 8 am 1 July 2010 and 1 July 2011. The volume in the pipe network was calculated based on the pipe lengths and nominal internal pipe diameters as recorded in the GIS database, assuming all the pipes were full. This includes both non-potable and potable water pipes.
Assumptions, Limitations, Caveats and Approximations
These data does not include service water storages or the pipe network managed and owned by Queanbeyan City Council (QCC). The QCC water supply system is much smaller in size than the ACTEW system and it is expected that the volume stored within the QCC tanks and pipes would be much less than that reported for ACTEW's system.
Data are measured, uncertainty is estimated at +/– 10%.
This line item corresponds to Line Item 5.1 Urban potable water supply system, reported in the 2010 Account. The following table presents substantive changes to the 2009–10 volume reported in the 2011 Account with the corresponding line item in the 2010 Account. The reasons for the changes, with their respective values, are detailed in the table and summarised hereafter: data are now available to estimate this volume. Given the minor change in volume that occurs from year to year within potable pipe networks, the National Water Account 2010 closing balance volumes were amended with these new data. These changes are summarised in the following table.
|Corresponding 2010 Account line item||Component||Value reported for the 2010 Account closing balance (ML)||Value difference due to scope change (ML)||Reported in the 2011 account for the 2010 account closing balance (ML)|
|Line item 5.1 Urban potable water supply system||Pipes||0||273||273|